“This is the easiest way possible to prevent an entirely predictable constitutional crisis," he said.

"When I press my friends who are Republican senators and leaders and say, ‘What would we do if he were to abruptly fire Robert Mueller,’ they say, ‘well, it’s not going to happen.’ " Coons said. "This is a simple step. … We could take up and pass this bill in a few minutes this afternoon and I’m confident it would get 60 votes.”

Flake has threatened to vote against any judicial nominee put forth in the lame-duck Senate session until the bill is voted on, giving Republicans no margin for error in their current 51-49 majority in the Senate and 11-10 majority on the Senate Judiciary Committee, on which Flake sits.

"We're whipping that to see where people are. I think the leader needs that information to decide how to manage all the competing demands on our time," Cornyn said when asked about discussions within the Republican caucus about the legislation.

Cornyn added Republicans were willing to hold a vote on the legislation "if that's what it's going to take" to move nominees.

“A number of senators of both parties have privately agreed that Whitaker is a less reliable supervisor and may well stumble into interfering with the Mueller investigation or may do it intentionally,” he said.

He touted in a 2017 interview that there was “no collusion” between the Trump campaign and Russia, adopting a favorite line from the president and undercutting the reason Mueller was appointed. He also said in 2014 that the courts were intended to be the "inferior" branch of government.

He wrote an op-ed for The Hill in May 2017 criticizing the idea of appointing a special counsel for the DOJ’s investigation.

“Serious, bipartisan congressional investigations into the Russian allegations have been under way for weeks and they have made progress. Hollow calls for independent prosecutors are just craven attempts to score cheap political points and serve the public in no measurable way,” he wrote.